Activities of leaves extracts of <i>Vernonia amygdalina</i> and <i>Abrus precatorius</i> against selected antibiotic resistant bacterial pathogens

Abstract

Ethanol and methanol extracts of Vernonia amygdalina and Abrus precatorius leaves were screened respectively against multi-antibiotic-resistant clinical isolates of Klebsiella pneumoniae, Salmonella enterica var. Typhi, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pneumoniae by agar-well diffusion method using graded concentrations of extract (200 mg/mL, 100 mg/mL, 50 mg/mL, 25 mg/mL, 12.5 mg/mL). Inhibition zone sizes (IZDs) produced by decreasing concentrations of V. amygdalina were recorded as Klebsiella pneumoniae (20 mm, 20 mm, 13 mm, 10 mm and 0 mm); Salmonella enterica var. Typhi (18 mm, 18 mm, 13 mm, 0 mm and 0 mm); Pseudomonas aeruginosa (18 mm, 18 mm, 13 mm, 0 mm and 0 mm); Staphylococcus aureus (15 mm, 15 mm, 10 mm, 0 mm and 0 mm); Streptococcus pneumoniae (17 mm, 17 mm, 15 mm, 0 mm and 0 mm). A. precatorius produced IZDs against Klebsiella pneumoniae (15 mm, 11 mm, 10 mm, 0 mm and 0 mm); S. enterica var. Typhi (16 mm, 13 mm, 9 mm, 0 mm and 0 mm); Pseudomonas aeruginosa (13 mm, 11 mm, 10 mm, 0 mm and 0 mm); Staphylococcus aureus (13 mm, 11 mm, 9 mm, 0 mm and 0 mm); Streptococcus pneumoniae (17 mm, 13 mm, 10 mm, 0 mm and 0 mm). The results suggest that extracts of V. amygdalina and A. precatorius leaves exert broad spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. These findings support the widespread use of the plants as local remedy for a variety of ailments, and indicate the potential roles of the plants in drug development programs of the pharmaceutical industry.